Please post your questions and answers to the
aprs.fi discussion group.
The group can be accessed using the web interface, RSS feed, or as a
regular mailing list.

How can I see my car's past positions (track history)?

Search for your car's callsign (or the ship's MMSI or name) in the map
view by entering it in the box labeled Seguir indicativo: - and
clicking the button labeled Buscar.

You have entered the tracking mode, and the vehicle's current position is now shown.
A little bit below the search box you should see the date browsing menu below the text
Escolher data:. Click on the year first, then month, and then the
day you're interested in.

You can also enter the tracking mode by clicking on
iniciar seguimento: in the info balloon after clicking on an icon
on the map.

The date browsing menu only shows the days when aprs.fi has received a
new position for the station.

Where is the displayed data obtained from?

The positions of the amateur radio operators and their vehicles are
received from the APRS-IS
network on the Internet. Most of them are originally transmitted on amateur
radio frequencies (typically around 145
MHz), and received and forwarded to the APRS-IS by
igate stations
run by clubs and individuals around the world.

The positions of ships are received from the
AIS
frequencies by receiving
stations around the world. If you wish to receive AIS transmissions and
provide them to the service, you're more than welcome to do
so.

How accurate is the position or speed data on aprs.fi?

Data accuracy varies greatly. Usually the data is fairly accurate, but quite
often it is not, and there are no guarantees that it would be valid
at all. It's trivial, on the AIS and amateur radio APRS networks,
to impersonate someone or send invalid data, it can
happen intentionally, and it often happens accidentally. A lot of data is
corrupted before it reaches the service - there is no end-to-end error
detection or real authentication in the APRS network.

For technical reasons (digipeater, igate, APRS-IS or aprs.fi issues)
position packets sometimes take minutes to
reach the service. Very frequently some GPS receivers give out incorrect position
fixes, and cars jump tens of meters or hundreds of kilometers away from
their real position. These jumps cause very strange speed readings.
GPS receivers are also pretty inaccurate when reporting altitude.

Specifically, the data is so inaccurate that it is in no way useful for
giving speed tickets. The service can be used for entertainment and hobby
purposes, it is not good for professional, governmental
or mission-critical use. Although the aprs.fi service is relatively stable and
usually accurate, the global APRS network is run by individual users on
their spare time, and it's availability, accuracy or performance is not
guaranteed.

Could you please delete my data from the service?

The data will be deleted automatically after 2 years. Some data will be
deleted earlier.

Email communications can be easily forged, and I have no
way of making sure you're really asking me to delete your data.
Also, I do not have much time to manually respond to requests by individual users -
there are tens of thousands of users who each have different kind of
unique needs. Instead, I prefer to use my time to develop
software features which benefit hundreds or thousands of users.

I won't be able to implement a software feature which would allow you to
delete your APRS data, since that would allow anyone to delete data
transmitted by someone else. There is no easy way to make sure you really
are who you claim you are.

Amateur radio transmissions are defined to be in the public domain (by
FCC rules in the US, and by respective legislation in most other countries,
and I suppose, by international regulations). Anyone can receive them, and
retransmit, publish or store them as they wish. If you do not wish your
position to be published on the Internet, the only guaranteed way is not to
transmit it.

How can I prevent my data from being displayed on this site?

If you wish to prevent your APRS data from entering the Internet, you can
append either NOGATE or RFONLY in your digipeater path.

If your current digipeater path is WIDE1-1,WIDE2-1 you need to
configure WIDE1-1,WIDE2-1,NOGATE as the path. If your current path is
WIDE2-2 you can use WIDE2-2,RFONLY.

Please note that there is no guarantee that everyone would obey the
NOGATE or RFONLY tags. If you really, really wish to protect your privacy
and avoid publishing your position on the Internet by someone, do not
transmit it at all.

Could you please implement feature X and fix bug Y?

Probably. Please submit your ideas on the
aprs.fi discussion group, or by
email (the address can be found in the blog's profile page). I'm very happy
to receive suggestions and I've implemented many of them. A lot of them are
in the "things to do" queue - things which I think I should do, but haven't
found the time to do yet. I always write the good ones down.

I try to first implement features which benefit as many users as
possible. Sometimes I implement features which I find the most interesting
for me personally. The selection is not entirely scientific or democratic.

Can I write software to download data from aprs.fi and display it on my site?

If the data is available through the API and the terms
are OK for your application, then the answer is yes. Otherwise, no.
If the data is not available through the API, please get in touch – maybe it can be added easily.

Downloading data for application use using the user interface
(for example, fetching the /info/ page just to get the current
coordinates of a station) wastes both human and computer resources.
First, you need to write a parser to extract
the data from the HTML (and then fix your parser every time I change my HTML layout). Second,
aprs.fi needs to do the user interface magic (language and timezone selection, user-friendly
template formatting, session set-up) for every request, all of which is unnecessary.
Third, the user interface
often generates much more information than you actually need. The position API responds in
a few milliseconds since the current positions are generally available in memory, while
the corresponding /info/ page can take tens or hundreds of milliseconds to generate because
it goes and finds the nearby stations, and the digipeaters and igates used, which often
requires disk access. All of this extra overhead consumes CPU time, which in turn
heats up the computer room, consumes electricity,
destroys tropical rain forests, accelerates global warming, and kills kittens. And baby seals.